14.3 Maintaining State

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	Webmaster in a Nutshell, 3rd Edition By Robert Eckstein, Stephen Spainhour
	Table of Contents
	Chapter 14.  The CGI.pm Module

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14.3 Maintaining State

One of the first complications for any nontrivial CGI script is how to "maintain state." Since HTTP is a stateless protocol, there's no built-in mechanism for keeping track of requests from the server end. A CGI transaction involving multiple forms, therefore, needs to find a way to remember information supplied on previous forms. One way to deal with this issue is to use cookies , which allow the CGI program to save information on the browser's end. HTTP Cookies are described in Chapter 17. CGI.pm uses the cookie( ) method to set and retrieve cookie information from a client.

CGI.pm implements other ways of maintaining state without cookies. To move around within a document containing form information, you can use the self_url( ) method to get a URL for the current document that saves the current form information. More generally , you can save query information from sessions in a variety of ways by saving to a filehandle with $query->save( ). This method provides the pathway to connecting client sessions with outside data sources like databases and user directories.

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